Re: how many use glue blocks
- From: nailshooter41@xxxxxxx
- Date: 24 Jan 2006 22:07:59 -0800
<<You using a smooth set of jaws? That's the reason I love my
or out; they _always_ line up properly.>>
I use pin jaws, dovetail jaws, and extended dovetail jaws on two
different VicMarc chucks I have. Maybe I should have been more
specific about this.
When the piece is off the chuck, depending on how green it is, how
humid it is, what kind of wood it is, etc, etc, the wood will move and
change shape unless it is some kind of kiln dried hardwood. I have had
pieces of persimmon LITERALLY crack open on the lathe from when I went
in for lunch and came back. Same with different other "found woods"
that I turn from swaps at the club meetings.
I almost always turn green wood, and if I am roughing one out and take
if off for a few days, no matter what your drying procedures are, the
wood will move, and it will be out of balance. The drier the wood is,
the less this should be a problem.
Indexing your chuck jaws will give you two things: letting your jaws
find their prevous seating with the parially crushed fibers having an
imprint for jaw faces to follow for alignment purposes, and second, the
opportunity for the jaws to have a similar from the pressure you exert
when tightening the chuck in the existing imprints, rather than cutting
new ones. The old imprints were cut into the wood and they reflect the
density of the wood, etc, which gives the amount of bite you get when
tightening the jaws. Many times a close inspection on some of the
curlier woods I turn will show that one side has deep imprints while
the other has amost none.
<<That's the reason I love my dovetails, in
or out; they _always_ line up properly. If you have 'em use the smooth
and make your tenon or recess just a tad bit bigger than the first
circularity on the jaws. They snug and draw real nicely to the
face that way. >>
Understood. However, I am not talented enough to exert exactly the
same amount of pressure on the chuck key every single time on each
piece of wood. When I started using this chuck I tore a bowl apart
using the dovetails, and twisted tenons beyond usefulness when
tightening overzealously. So the chuck holds just fine whether using a
dovetail recess or a tenon or "spigot".
But my wrists are not sensitive enough to be able to discern from one
day to the next if I am turning at 55:1 or 57:1 to get exactly the same
amount of holding pressure. Sometimes I really clamp down, sometimes I
barely exert enough pressure to hold the piece, other times I just
forget how hard I clamped it.
And as another thought, I think it depends on how accurate you want
things to be in regards to what you are doing. When I am cutting
something small (like the 3/16 ebony inserts on my curly maple
earrings) I want every edge I can get. Even grasping the short tenon I
glue them to can change its balance when off and on the chuck again by
1/32 or so. And with 1/32 off center, that give a total of 1/16
eccentricity which will goof me up if I have already cut the diameter
of the piece to size for use.
When I am turning bowls or vases, I do it as a matter of habit. But if
they have been under the shed for 6 months after roughing out, and for
some of the pieces, just overnight, it really doesn't matter as they
will be plenty out round and balance from drying and the released
tensions in the wood.
But for me, and I do understand YMMV, I will take a second where I can
to help me along a little easier.
I also do the same thing with my faceplates. I have taken a small
metal file and put a notch into the metal so I can line up glue blocks
to near perfect balance when remounting, and for then again, "X" marks
the spot on the project to line up the faceplate when remounting. This
will make a >huge< difference in getting your piece back on correctly.
Annnnd.... you guessed it. I also do it with my spur drive.
Remounting a spindle turning on the spur is a snap for almost perfect
balance when you put it back on exactly the way it came off.
Just things to think about...
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